Where To Get High Octane Gas...
In west Michigan US131, D-ave exit just south of US131 Dragway both the Citgo station on the west side and BP station on the east side of the exit sell 110 octane. BP's is Torco brand and Citgo's I'm not sure. Last I fueled up it was $4.59/gallon.
One tip: If you find yourself there, use the BP station. You can park in the gravel drive 5ft from the pump and your not on BP property. You can walk across the grass, fill your cans, then dump them into you car since your car's not on BP property and your not fueling your car at their station which is unlawful. Just dont let the cops see you or you may get busted...